export interface TicketReplyRecord {
	id: bigint;
	userId: number;
	content: string;
	createdAt: Date | null;
}

export interface TicketReplyDb {
	findTicket(
		ticketId: bigint,
	): Promise<{ id: bigint; userId: number | null } | null>;
	createReply(data: {
		ticketId: bigint;
		userId: number;
		content: string;
		createdAt: Date;
		updatedAt: Date;
	}): Promise<TicketReplyRecord>;
	touchTicket(ticketId: bigint, updatedAt: Date): Promise<unknown>;
}

export const MAX_UNSIGNED_TICKET_ID = 18_446_744_073_709_551_615n;

function boundedDecimalPattern(maximum: string): RegExp {
	const alternatives = [`[1-9]\\d{0,${maximum.length - 2}}`];
	for (let index = 0; index < maximum.length; index += 1) {
		const maximumDigit = Number(maximum[index]);
		const minimumDigit = index === 0 ? 1 : 0;
		const upperDigit = maximumDigit - 1;
		if (upperDigit < minimumDigit) continue;
		const digit =
			upperDigit === minimumDigit
				? String(minimumDigit)
				: `[${minimumDigit}-${upperDigit}]`;
		alternatives.push(
			`${maximum.slice(0, index)}${digit}\\d{${maximum.length - index - 1}}`,
		);
	}
	alternatives.push(maximum);
	return new RegExp(`^(?:${alternatives.join("|")})$`, "u");
}

export const CANONICAL_TICKET_ID_PATTERN = boundedDecimalPattern(
	MAX_UNSIGNED_TICKET_ID.toString(),
);

// Canonicalize a SQL BIGINT identifier without passing through Number.
export function canonicalTicketId(value: string | number | bigint): bigint {
	let parsed: bigint;
	try {
		if (typeof value === "bigint") {
			parsed = value;
		} else if (typeof value === "string") {
			if (!CANONICAL_TICKET_ID_PATTERN.test(value)) {
				throw new Error("noncanonical identifier");
			}
			parsed = BigInt(value);
		} else if (Number.isSafeInteger(value) && value > 0) {
			parsed = BigInt(value);
		} else {
			throw new Error("unsafe identifier");
		}
	} catch {
		throw new Error("invalid ticket identifier");
	}
	if (parsed <= 0n || parsed > MAX_UNSIGNED_TICKET_ID) {
		throw new Error("invalid ticket identifier");
	}
	return parsed;
}

export async function createOwnedTicketReply(
	db: TicketReplyDb,
	input: { ticketId: bigint; userId: number; content: string },
): Promise<TicketReplyRecord | null> {
	const ticket = await db.findTicket(input.ticketId);
	if (!ticket || ticket.userId !== input.userId) return null;

	const now = new Date();
	const reply = await db.createReply({
		...input,
		createdAt: now,
		updatedAt: now,
	});
	await db.touchTicket(input.ticketId, now);
	return reply;
}